Method of making heat or flame detecting elements



May 19, 1953 D. R; SQUIER- METHOD oF MAKING HEAT 0R FLAME DETECTINGELEMENTS Filed Nov. 17, 1949 tungst- IN VEN TOR j 00A/ALD Rspu/ERrroRA/EY Patented May 19, 1953 METHOD OF MAKING HEAT OR- FLANULlDETECTING ELEMENTS` Donald R. Squier, Pompton Plains, N. J., assignor toSpecialties Development Corporation, Belleville, N. J., a corporation ofNew Jersey Application November 17, 1949, Serial No. 127,845

14 Claims.

The present invention relates to a method of making heat or flamedetecting elementsJ and, more particularly, relates to a method ofmaking elements such as illustrated and described in my co-pendingapplication for United States Letters Patent, Serial No. 115,594, ledSeptember 14, 1949, now Patent No. 2,587,916.

The invention is primarily concerned with the making of the heatsensitive elements for heat or flame detecting cables of the typegenerally comprising an elongate tube or housing, one or moreelectrically conductive Wires disposed in the tube, and a covering offiber glass yarn on the Wires which is practically non-conductive atnormal temperatures but is rendered conductive at much highertemperatures, whereby the wires in effect are insulated from each otherand/or the tube at normal temperatures and an electrical circuit isestablished between the Wires and/or the tube at higher temperatures.

method of making such heat or flame detecting elements.

Another object is to provide a method of the foregoing character whichfacilitates adjusting the electrical properties of the covering and/orimproving its high temperature withstanding qualities.

A further object is to provide a method of the foregoing character forproducing covered wires which may be immediately inserted into tubes ormay be conveniently stored for use in the future.

Other and further objects of the invention will be obvious upon anunderstanding of the illustrative embodiment about to be described, orwill be indicated in the appended claims, and various advantages notreferred to herein will occur to one skilled in the art upon employment-of the invention in practice.

-to withstand high temperatures, and drying and/ or sintering thetreated covering. The elements produced by the foregoing process may beinserted into tubes immediately or may be stored `for use in the futureb-y Winding the same on spools or drums or the like.

In the drawing:

Figure l is a diagrammatic flow chart illustrating a method of makingthe elements in accordance with the present invention.

Figure 2 is a fragmentary elevational view of a length of wire or thelike.

Figure 3 is a fragmentary elevational View of the wire having a braidedfiber glass yarn covering thereon.

Figure 4 is a fragmentary elevational View of the wire having a spirallyWound fiber glass yarn covering thereon.

Figure 5 is a cross-sectional view illustrating the covering and wireshown in either Figure 3 or Figure 4.

Figure 6 is a cross-sectional View` illustrating the covered wire shownin Figure 5 disposed in a tube.

Figure is a View similar to Figure 6 with the diameter of the tubereduced.

Referring to the drawing, and more particularly to Figure 1 thereof,there is shown a diagrammatic flow sheet illustrating a method of makingheat or flame detecting elements in accordance with the invention. Anelectrical'conductor, such as Wire IB (Figure 2), is supplied from asource such as a spool or drum and is delivered to a machine forproviding a fiber glass yarn covering thereon. Such a machine may be ofthe type which braids the yarn on the wire lil to provide a braidedcovering Il (Figure 3) or of the typewhich spirally Winds the yarn or astrip or tape of yarn to provide a wound covering I2 (Figure 4). Ineither instance, a porous fiber glass fabric covering is applied to thewire.

The fiber glass yarn may be of any composition, although yarns made ofboro-silicate or barium type glass fibers are preferred because of theirrelatively high softening point temperatures and thermal endurancewithout material variation in physical or chemical characteristics uponrepeated changes in temperature over a wide range. Such glasscompositions have negative temperature coemcients of resistivity whichenable the fiber glass covering to act as an insulator at normalatmospheric temperatures and to act as a conductor of electricity uponbeing subjected to flame or heat produced by flame.

It has also been found suitable to utilize fiber glass yarn which hasbeen treated in a 15% hydrochloric acid solution at about F. Suchtreatment is believed to remove lead oxide from the glass and therebyraise the softening point temperature of the glass composition.

The covered wire is then delivered to apparatus for applying a materialadapted to give the covering desired heat detecting characteristics,such as the ability to withstand temperatures approaching 2000 F. andhigher, and/or a predetermined desired negative temperature coefficient.

The covering may be improved to resist high temperature by coating orimpregnating the saine with a slurry of refractory material orcompositions of two or more refractory materials. Such materials may becomplexes or compounds of aluminum oxide, aluminum silicate, calciumoxide, chromic oxide, chromite, magnesium oxide, magnesium silicate,silicon carbide, titanium xide, zirconium oxide and'zirconium carbideand the like.

These materials or compositions thereof may contain other compounds insmall percentages Without materially aiecting the refractory propertiesthereof. For example, small amounts of carbonatos are no-tobjectionable, but, to the contrary, are desirable to provide a iluxingaction in the event it is desired to sinter the refractory materials andthe glass libers.

Various commercially available prepared refractory type cements may beutilized to good advantage for improvingthe yarn to withstand hightemperatures.

Graphite of the refractory type may be also utilized, but, due to itsrelatively high electrical conductivity, its use in small amounts or inmixtures comprising a major proportion oi less conductive refractorymaterials is recommended.

Since refractory materials have negative temperature coefficients ofresistivity, they may also be applied to the covering for the purpose ofmodifying the resistivity thereof whereby the covering becomesrelatively conductive at predetermined temperatures.

The resistivitl7 of the covering, either with or without application ofthe refractory material, may be modined or adjusted to a predeterminedvalue by the application of materials having thermistor-like properties.Such materials may be oxides of barium, beryllium, cadmium, cerium,cobalt, copper, iron, lead, manganese, nickel, strontium, tin andtungsten and the like. These materials may be applied in slurry form ormay be incorporated in the slurry o f refractory materials.Alternatively, suitable salts of these metals in a solvent may beapplied to. the covering or may be incorporated with the refractorymaterial, which thereafter are converted into the oxide of the, metal.

The so treated covered wire is then delivered to a drying zone Where theliquid or solvent of the slurry or solution is removed by theapplication of heat at a temperature well above the boiling point ofWater.

The Wire (Figure 5) is `finally delivered to. a zone maintained attemperatures adapted to effeot sintering of the refractory material andglass bers and/or the conversion of metallic salts to oxides of themetals. `Sintering apparently produces a glass-refractory compositionwhich may be alternately and repeatedly subjected to temperaturesvarying between about 70 F. and about 2000 F. Without any materialvariation in temperature coeflicient of resistivity.

The element' produced by the foregoing described method is now ready tobe cut in lengths and inserted into a tube lll havingan inner diameterwhich is greater than the diameter of the element (Figure 6), and thetube may then be :reduced in diameter, for example, by redrawing thesame to snugly house lthe element (Figure '1).

4 Alternatively, the element may be wound on a drum or spool or thelike, and stored for future use in a compact and convenient manner.

From the foregoing description, it will be seen that the presentinvention provides a simple, economical and practical process forproducing heat or flame detecting elements wherein all of the steps maybe performed in line sequence from the bare Wire to the insertion of thetreated covered Wire into the tube or housing. The method of thisinvention has great utility because it can be carried out in a minimumamount ofY oor space and at all times leaves the Wire in a iiexiblecondition to facilitate handling and storage thereof.

As. various changes may be made without departing from the spirit andscope of the invention and without sacricing any of its advantages, itis to be understood that all matter herein is to be interpreted asillustrative and not in any limiting sense.

I claim:

l. A method of making continuous flexible heat or name detectingelements of the class described, which comprises applying a continuousflexible covering of ber glass yarn to an electrically conductiveflexible Wire, and applying a material to the covering adapted to. givethecovering desired heat detecting characteristics said material being asubstance selected from the group consisting of aluminum oxide, aluminumsilicate, calcium oxide, chromic oxide, chromite, inagnesiuzn oxide,magnesium silicate, silicon carbide, titaniumk oxide, zirconium oxideand zirconium carbide.

2. A method of making continuous flexible heat or aine detectingelements of the class described, vvhich comprises applying a continuousexible covering of liber glass. yarn to; an electrically conductiveilexible wire applying a ma,- `terial to thev covering adapted to,y givethe covering desired heat. detecting characteristics, and drying thecovering said material being; a. Sub,.- stance selected from the groupConsisting; of aluminum oxide, aluminum silicate, calcium oxide, chromicoxide, chrorrite,l maeglsiumoxide, magnesium silicate, silicon carbide,titanium oxide, zirconium oxide and; zirconium carbide.

3. A method of making continuous exible heat 0r flamcvdctectine elementscf the class described, which comprises applying a continuous exiblecovering of fiber glass to anelecl'fricall-yl con-- ductive flexiblewire, applying a material to- `the covering adapted t give the coveringdesired heat detecting characteristics, and winding the coveredwire saidmaterial being al substance se,- lected from the group, consisting ofaluminum oxide, aluminum silicate, calciumox'ide, chromic oxide,chrrnite, magnesium oxideL magnesium silicate, silicon carbide, titaniumOxide, Zirconium oxide and zirconium Carbide.

4. A method of Amaking continuous ilexible heat or flamedetectingelements otA the class described, Whlch comprises. applying acontinuous iiexible covering of ber glass, yarn to .an electricallyconductive flexible Wire, applying a materiall ,17.0, .the coveringadapted to give the, covering desired heat detectingv characteristics,drying the cove-ring, and Winding the covered Wire said material being asubstance yselected from the grou-pconsisting of aluminum oxide,`alu-mimirn silicate, calcium oxide., chromic oxide, chromite, magnesiumoxide, masnesiumsilicate, silicon carbide, titanium oxide, zirconiumoxide and zirconium carbide.

5. A method of making continuous flexible heat or liarne detectingelements of the class described, which comprises braiding a continuousflexible covering of ber glass yarn on an electrically conductiveflexible wire, and applying a material to the covering adapted to givethe covering the desired heat detecting characteristics said materialbeing a substance selected from the group consisting of aluminum oxide,aluminum silicate, calcium oxide, chromic oxide, chromite, magnesiumoxide, magnesium silicate, silicon carbide, titanium oxide, zirconiumoxide and zirconium carbide.

6. A method of making continuous flexible heat or flame detectingelements of the class described, which comprises spirally winding acontinuous flexible covering of fiber glass yarn on an electricallyconductive flexible wire, and applying a material to the coveringadapted to give the covering the desired heat detecting characteristicssaid material being a substance selected from the group consisting ofaluminum oxide, aluminum silicate, calcium oxide, chromic oxide,chromite, magnesium oxide, magnesium silicate, silicon carbide, titaniumoxide, zirconium oxide and zirconium carbide.

7. A method of making continuous exible heat or flame detecting elementsof the class described, which comprises applying a continuous exiblecovering of fiber glass yarn on an electrically conductive flexiblewire, and applying a material having a nega-tive temperature coefficientof resistivity to the covering said material being a substance selectedfrom the group consisting of aluminum oxide, aluminum silicate, calciumoxide, chromic oxide, chromite, magnesium oxide, magnesium silicate,carbide, titanium oxide, zirconium oxide and zirconium carbide.

8. A method of making continuous flexible heat or flamedetectingelements of the class described, which comprises applying acontinuous flexible covering of fiber glass yarn on an electricallyconductive exible wire, and applying a slurry of refractory material tothe covering to enable the covering to withstand relatively high ftemperatures said material being a substance selected from the groupconsisting of aluminum oxide, aluminum silicate, calcium oxide, chromicoxide, chromite, magnesium oxide, magnesium silicate, silicon carbide,titanium oxide, zirconium oxide and zirconium carbide.

9. A method of making continuous flexible heat or flame detectingelements of the class described, which comprises applying a continuousflexible covering of fiber glass yarn on an electrically conductiveflexible wire, and impregnating the covering with a thermistor-likematerial said material being a substance selected from the groupconsisting of aluminum oxide, aluminum silicate, calcium oxide, chromicoxide, chromite, magnesium oxide, magnesium silicate, silicon carbide,titanium oxide, zirconium oxide and zirconium carbide.

10. A method of making continuous fiexible heat or flame detectingelements of the class described, which comprises applying a continuousflexible covering of fiber glass yarn on an electrically conductiveflexible Wire, impregnating the covering with a thermistor-likematerial, and coating the covering with a refractory material saidmaterial being a substance selected from the group consisting ofaluminum oxide, aluminum silicate, calcium oxide, chromic oxide,chromite, magnesium oxide, magnesium silicate, silicon carbide, titaniumoxide, zirconium oxide and zirconium carbide.

11. A method of making continuous flexible heat or flame detectingelements of the class described, which comprises applying a continuousflexible covering of fiber glass yarn on an electrically conductiveflexible wire, applying a slurry of refractory material to the covering,and sintering the covering and material to produce a composition adaptedto withstand relatively high temperatures said material being asubstance selected from the group consisting of aluminum oxide, aluminumsilicate, calcium oxide, chromic oxide, chromite, magnesium oxide,magnesium silicate, silicon carbide, titanium oxide, zirconium oxide andzirconium carbide.

l2. A method of making continuous flexible heat or flame detectingelements of the class described, which comprises applying a refractorymaterial to a continuous flexible fiber glass yarn covering on anelectrically conductive flexible wire, and sintering the refractorymaterial and the ber glass yarn to produce a composition adapted towithstand relatively high temperatures said material being a substanceselected from the group consisting of aluminum oxide, aluminum silicate,calcium oxide, chromic oxide, chromite, magnesium oxide, magnesiumsilicate, silicon carbide, titanium oxide, zirconium oxide and zirconiumcarbide.

13. A method of making continuous flexible heat or flame detectingelements of the class described, which comprises impregnating acontinuous iiexible fiber glass yarn covering on an electricallyconductive flexible wire with a thermistor-like material said materialbeing a substance selected from the group consisting of aluminum oxide,aluminum silicate, calcium oxide, chromic oxide, chromite, magnesiumoxide, magnesium silicate, silicon carbide, titanium oxide, zirconiumoxide and zirconium carbide.

14. A method of making continuous flexible heat or flame detectingelements of the class described, which comprises impregnating a con-'tinuous flexible fiber glass yarn covering on an electricallyconductive flexible wire with a thermistor-like material and arefractory material, and sintering the refractory material and the glassyarn covering to produce a composition adapted to withstand relativelyhigh tempera-x tures said material being a substance selected from thegroup consisting of aluminum oxide, aluminum silicate, calcium oxide,chromic oxide, chromite, magnesium oxide, magnesium silicate, siliconcarbide, titanium oxide, zirconium oxide and zirconium carbide.

DONALD R. SQUIER.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 2,370,046 Keyes Feb. 20, 1945 2,372,840 Mattern Apr. 3, 19452,390,039 Slayter et al. Nov. 27, 1945 2,427,507 Powell et al. Sept. 16,1947 2,487,526 Dahm Nov. 8, 1949

1. A METHOD OF MAKING CONTINUOUS FLEXIBLE HEAT OR FLAME DETECTING ELEMENTS OF THE CLASS DESCRIBED, WHICH COMPRISES APPLYING A CONTINUOUS FLEXIBLE COVERING OF FIBER GLASS YARN TO AN ELECTRICALLY CONDUCTIVE FLEXIBLE WIRE, AND APPLYING A MATERIAL TO THE COVERING ADAPTED TO GIVE THE COVERING DESIRED HEAT DETECTING CHARACTERISTICS SAID MATERIAL BEING A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ALUMINUM OXIDE, ALUMINUM SILICATE, CALCIUM OXIDE, CHROMIC OXIDE, CHROMITE, MAGNESIUM OXIDE, MAGNESIUM SILICATE, SILICON CARBIDE TITANIUM OXIDE, ZIRCONIUM OXIDE AND ZIRCONIUM CARBIDE. 